#include "stdstuff.h"
#include "LibraryCard.h"

// constructs a LibraryCard object (for a patron).  The patron is allowed up to 20 books and currently has none borrowed.
LibraryCard::LibraryCard() {
   maxBooks = 20;
   numBooks = 0; // no books out
}

// constructs a LibraryCard object (for a patron).  The patron is allowed to borrow up to the given number of books, and
// currently has none signed out.
// Throws invalid_argument exception if argument is less than or equal to 0.
LibraryCard::LibraryCard(int maxBooks) {
   if (maxBooks <= 0) { // **must** initialize fields for full marks
      this->maxBooks = 20;
      numBooks = 0; // no books out
      // I chose to use the default -- doesn't matter as long as they are initialized to something reasonabls
      throw invalid_argument("LibraryCard::LibraryCard - maxBooks must be greater than 0");
   }
   this->maxBooks = maxBooks;
   numBooks = 0; // no books out
}

// numBooks books are signed out on the given library card.
// if numBooks will cause the patron to have more than the maximum number of books, this method has no effect.
// Throws invalid_argument exception if argument is less than 0.
void LibraryCard::borrowBooks(int numBooks) {
   if (numBooks < 0) throw invalid_argument("LibraryCard::borrowBooks - numBooks must be greater than or equal to 0");
   if (numBooks > maxBooks-this->numBooks) return; // attempt to take out too many books
   this->numBooks += numBooks;
}

// numBooks books are returned on the given library card.
// if numBooks is larger than the number of books this patron has, this method has no effect.
// Throws invalid_argument exception if argument is less than 0.
void LibraryCard::returnBooks(int numBooks) {
if (numBooks < 0) throw invalid_argument("LibraryCard::returnBooks - numBooks must be greater than or equal to 0");
   if (numBooks > this->numBooks) return; // attempt to return too many books
   this->numBooks -= numBooks;
}

// prints the number of books that this LibraryCard has currently signed out.
// (Does not change the state of the LibraryCard.)
void LibraryCard::booksOut() const {
   cout << numBooks;
}

// returns the percent level of the LibraryCard usage, i.e. 100 = max number of books signed out; 0 = no books signed out, etc.
// (Does not change the state of the LibraryCard.)
double LibraryCard::currentUsage() const {
   return 100.0 * numBooks / maxBooks;
}